304 ss cracking

By clint thompson Date 04-27-2009 16:19

I have been fixing a 304 ss 10,000 gal. tank and the only thing I can come up with is the tank had caustic in it since the 1960's and it has been empty for 5 years now, when the tank was off loaded they droped it on the bottom flange and the metal in the bottom of the tank has many spider web cracks around the old flange.

I have cut out the old flange and cleaned up around it still finding cracks in the metal so I cut out another 1 1/4" now having a 14" hole in the tank. I have welded a piece of the patch material to the old tank material both 304 ss and I hit the old pc with a hammer just to show the company that the tank bottom was no good and it just cracked open the small cracks again the metal is just brittle.

I guess what I want to know is what would you suggest about the tank? Is the tank not worth fixing or is there something that I can do for the company?

Thanks
ct

By GRoberts (***)

Date 04-28-2009 00:12

Without knowing the details about the environment (i.e. temperature, pH, chloride concentration), it can be hard to tell the cause, but caustic cracking is one possible cause. The only solution would be to cut out any damaged metal and replace. If you have access to the inside of the tank, do a thorough PT inspection to find the extent of the problem before deciding if any of it is worth repairing or not

By MBSims

Date 04-28-2009 01:17

You definitely need to do some NDE before using this tank. Stress corrosion cracking is a distinct possibility with 304 SS, especially if it's not 304L. As Greg recommended, liquid penetrant testing from the inside surface would be the best way to detect this type of cracking without breaking the bank. Focus around all weld seams and welded attachments.

By clint thompson Date 04-28-2009 01:54

Thanks for the info I looked over the other areas of the tank by the other welds and it looks like it has the stress marks in it to. I think it is a matter of time till they start having trouble in other areas.

Thanks again.
CT

By vittorio (*)

Date 05-08-2009 06:28

you could also make some lab analysis of the piece of metal with the cracks and see if there are also chlorides or other chemicals.. this can give you a better figure of what happened

V.